Spurs are interested in Fiorentina defender Nikola Milenkovic.
With doubts remaining over the future of Toby Alderweireld, Tottenham are among a number of clubs tracking the 20-year-old Serbian.
Alderweireld has just a year left on his current contract.
Spurs have an option to extend it until 2020, but a clause means the Belgium international centre-back could still leave next summer for a fee of just £25million.
Manchester United — where Serb centre-back Nemanja Vidic is a club legend — are already big admirers of his talent, to potentially reunite him with international team-mate midfielder Nemanja Matic.
The former Partizan Belgrade star, currently on international duty, and moved to Florence-based Fiorentina last year for just £4m and and has since attracted high praise with his displays in Serie A.
This season, Milenkovic has played eight times, helping keep three clean sheets while also scoring twice himself.
Alderweireld fuelled speculation over a Tottenham exit by admitting earlier this week he is "not thinking" about signing a new deal.
The 29-year-old was strongly linked with a move to Man United over the summer as Jose Mourinho looked to take a new centre-half to Old Trafford, only for the Reds to baulk at Spurs' £65m valuation.
There had been speculation Alderweireld would pen fresh terms after an impressive start to the season, but he insists an extension is not in his thoughts.
"Honestly, I’m not thinking about it at the moment," he said.
"I feel good and I’m playing so I’m happy. We’ll see what happens."